The New York Police Department puts an endless list of tasks on the shoulders of its so-called white shirts — the commanders atop an army of lesser-ranking officers in dark blue.

But the portfolio of the white shirt has now unexpectedly grown to include the role of enforcer.

As the Occupy Wall Street protests, which began on Sept. 17, lurch into their third week, it is often the white shirts who lay hands on protesters or initiate arrests. Video recordings of clashes have shown white shirts — lieutenants, captains or inspectors — leading underlings into the fray.